Learning about Light 101 - Assignment 1 - 3/15/10 - 3/28/10

Discussion in 'Photography Beginners' Forum' started by Village Idiot, Mar 15, 2010.

  1. Village Idiot

    Village Idiot No longer a newbie, moving up!

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    Requirements:
    1 flash
    1 lighting modifier that diffuses light (umbrella, softbox, etc... Not a Fong Dong or similar device)
    1 way to trigger the device off camera
    1 light stand
    Basic knowledge of camera operation and how ISO, shutter speed, and aperture work together.

    This is going to be an open ended type of experiment. I'm not asking for a limit on participants or that everyone participates for every single bi-weekly assignment. This is for fun and for learning your equipment.

    Please post all finished products for this assignment in this thread for review and keep everything friendly.

    Assignment 1 - Ambient vs. Artificial:

    I'll say that I think of of the most valuable pieces of knowledge for being able to use flash, whether it off camera or on camera, and it's practical use in day to day photography is the ability to know when to use ambient and artificial together along with the ability to know when to separate those two for desired effects.

    Now that I'm done with that run on sentence:

    This assignment will focus on being able to know how to control your flash to either balance or kill ambient light. Depending on how powerful your flash is will determine your working environment. Most all strobes should be able to overpower your typical indoor lighting, be it incandescent or flourescent bulbs. If you were to move outside in bright mid day sun, you'd need a much more powerful light like a 400w/s mono light.

    To be able to work with balancing ambient and flash, you'll have to understand that you're essentially getting two separate exposures when using a flash. You're getting the ambient light that's let in during the time that the shutter is open and you're getting the light that falls on the subject from the flash itself.

    There are three things to consider: ISO, shutter speed(ss), and aperture. ISO, ss, and aperture control ambient lighting while ISO and aperture will control the flash exposure. Everyone should already know how to control an ambient exposure based on ISO, ss, and aperture. When you add flash to the mix, the ss will do nothing to increase or decrease* the exposure level of the flash. To adjust that, you'll have to either raise or lower the power of the flash itself, or adjust the aperture to control how much light is let into the camera itself.

    This is particularly useful when trying to photograph a subject in a large area where flash fall off could cause the subject to be properly exposed while the ambient would have been killed. This is something you will see a lot with P&S cameras when people take photos in dark environments. For a scene like this, you would manually adjust the exposure settings on the camera to expose for ambient and then set your flash power properly expose your main subject.

    The above scenario can be taken a step farther to make an overly dramatic photo in a normally dull envrionment. Say you're outside on a sunny day and you have a flash powerful enough to overpower the ambient. You could take a photo of the subject with a fast enough ss, low ISO, and a narrow aperture to under expose the ambient anywhere from a minor amount of 1 stop, to 3-4 stops where is would make your 12:00 noon shoot look like it was done at dusk.

    This can also be applied to a scene where you want to shoot a subject, but want no ambient light. If you can get a photo where you can totally under expose the ambient light (which is easiest when you're shooting at dusk or indoors), you can use the light from your flash to provide the only light that will expose the subject. This is useful when shooting in evironments where different light sources have different color temperatures** and where stopping movement of the subject will be necessary.

    One last important piece of information*, the max sync speed (often called x sync) of most modern DSLR cameras averages about 1/200 shutter speed. You can find the specific x sync of your particular camera in it's manual or by searching online. Many things can effect the x sync, ranging from whether the flash is proprietary or third party, the method of firing the flash (on camera or off, with a sync cable or with triggers), the size of the sensor and the design of the camera itself, as well as other factors. When you start to go over the x sync* you will notice a black bar creeping across the exposure. This is from the way that the shutter operates and not being fully open while the flash fires. This means when balancing ambient an flash, you often have to work with narrowing the aperture to help kill ambient rather than just jacking up the ss.

    For this assignment, those who wish to participate will provide three photos of the same subject. Those three photos will be one photo of the photo properly exposed by ambient light, one photo of the subject properly exposed by ambient and flash, and one photo of the subject in the same ambient light, but just exposed by the flash.

    If you have additional questions, feel free to post them. I'll try and post up example photos ASAP. I'm going to be really busy all week, but I'll see what I can squeeze in.

    *Certain cameras and techniques will allow you to shoot over the camera's x sync without getting the black bar. For sake of learning and understanding the concepts, keep your camera under it's x sync.

    **If you have question about this, ask. It will be covered in a future lesson though.

    The group URL:
    http://www.thephotoforum.com/forum/groups/learning-about-light.html
     
    Last edited: Mar 16, 2010
  2. Village Idiot

    Village Idiot No longer a newbie, moving up!

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    Ambient
    1/40
    f/4
    ISO 3200

    I had to jack the ISO up to get a decent shutter speed. I was using a canon 17-40 and f/4 is the fastest aperture available.

    [​IMG]

    Ambient and flash
    1/40
    f/4
    ISO 3200
    Canon 580EX II at 1/128 power

    I used the same settings for ambient and had to set the flash to it's lowest power to get it to work. The Problem is that if I needed to go any lower for the ambient with the flash, I couldn't power it down. However, there is a way to remedy this situation. If you move the flash farther away from the subject, it decreases the amount of light that falls on the subject. It's due to the inverse square law.* All I would have to do is start moving the flash away from my subject to decrease the exposure on it/them.

    [​IMG]

    Flash 1
    1/40
    f/4
    ISO 100
    fp 1/128

    This is straight flash with the ambient killed. I dropped the ISO from 3200 to 100. That's 5 stops of light less than the above exposure. The ISO is the only difference between the two photos and as you can see I have almost completely killed the ambient as well as the exposure from the flash.

    [​IMG]

    Flash 2
    1/40
    f/4
    ISO 100
    fp 1/4

    OK, I'm back to being exposed properly with the ambient remaining the same as in the previous photo. What I did was increase the flash power 5 stops from 1/128 to 1/4. That's 5 steps from 1/128 to 1/64 to 1/32 to 1/16 to 1/8 to 1/4. Increasing the power by each stop is doubling the amount of light the flash puts out. I compensated 5 stops of ISO to 5 stops of flash power. This kills off the ambient by decreasing the ISO and exposes the subject with just the flash by increasing the power.

    [​IMG]

    Flash 3
    1/40
    f/8
    ISO 100
    fp 1/1

    Let's murder the ambient! I increased the aperture by two stops; f/4 to f/5.6 and then f/5.6 to f/8. That completely kills any ambient light. To compensate, I upped the power of the flash two stops. It goes from 1/4 to 1/2 and then from 1/2 to 1/1 keeping me exposed the same throughout all of the photos that have the flash on me.

    [​IMG]

    Keep in mind that stops are different between equipment, so upping the power 3 stops on a flash while closing the aperture down 3 stops on the camera may show some minor discrepancies between exposures. It should be off by much at all, but occasionally you may see a difference between exposures.

    *http://en.wikipedia.org/wiki/Inverse-square_law
    Basically states that an object half the distance from the source of the light will receive a quarter of the amount of the illumination. An object at 4' from a flash that's properly exposed at 1/4 power would need 1/1 power at 8' from the source to be properly exposed.
     
    Last edited: Mar 23, 2010
  3. LBPhotog

    LBPhotog TPF Noob!

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    Hey, VI, just a quick question.

    When using the combination of availible and artificial light isn't that going to be a white balane nightmare? Or is that part of the task too?
     
  4. Village Idiot

    Village Idiot No longer a newbie, moving up!

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    It depends on the light sources. But that's something that's going to be covered in a future assignment, so for now it's OK.
     
  5. Dao

    Dao No longer a newbie, moving up!

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    Interesting ... Let me find sometimes this week.
     
  6. Olympus E300

    Olympus E300 TPF Noob!

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    I guess I must be a real newb!! I'm waiting for the examples so I can better understand the concept...
     
  7. LBPhotog

    LBPhotog TPF Noob!

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    Submission, (and hopefully a decent enough example - and hopefully done CORRECTLY ... :lol:)

    Image #1 - Entire image is exposed by the two windows the CAMERA RIGHT

    [​IMG]
    (ISO 200 1/125 @ f/3.2)

    Image #2 - Entire image is exposed via one 800 watt strobe CAMERA RIGHT

    [​IMG]
    (ISO 200 1/200 @ f/6.3

    Image #3 - Image is exposed via both ambient light from window right (mostly for fill) and 800 watt strobe.

    [​IMG]
    (ISO 200 1/60 @ f/5 and yeah, she was crying .. it was getting to be nap time)

    I hope this is what VI is looking for, and I hope these are done correctly.
     
    Last edited: Mar 17, 2010
  8. RONDAL

    RONDAL TPF Noob!

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    i'll bite.
    and i'll state right now its outside of the specified date range by a bit, but its more a kick off with an explanation to be used as an example. If i find time in the next few days (busy moving) i'll shoot some more stuff.

    The photo:

    [​IMG]

    exif data: http://farm3.static.flickr.com/2497/3768260186_a356c37613_b.jpg


    How i did the shot:

    camera was a nikon d90 with a 50mm f1.8 lens
    i am using cybersync's to trigger the flash remotely.

    i have a 60" shoot through umbrella camera & subject right with an sb600 in it at 1/2 power.

    I shot in manual at a shutter speed of 1/250th which is also my max sync speed. I did this to kill ambient and get the dramatic skies in the background. Had i shot at a 1/100 or thereabouts the sky would just be grey and orange, and you wouldn't see the clouds as dramatically.

    I then adjusted the aperture until i got the desired exposure on the subject.


    Just to give a second example.....when you might NOT want to use your max sync speed:

    [​IMG]

    exif http://farm3.static.flickr.com/2534/3751770078_565f2331bb_b.jpg


    This was shot at like 1/5th of a second I believe. It was really dark when i was shooting and by getting the longer shutter speed that wasn't at max sync i could allow the sky to actually show all of the colors rather than just being black. had i sync'd at max speed i would have only been lighting the car.

    Note there is actually 3 lights being used in this shot.
    x1 60" shoot through umbrella SB600 @ 1/1 power camera left
    x1 60" shoot through umbrella SB600 @ 1/1 power camera right
    x1 SB-24 (i think) at 1/1 pointed at the building so i could light that and show some detail in the background building that would otherwise be a silhouette.
    All triggered via cybersyncs.



    I hope this helps explain the original post for those that were maybe not understanding it as well. This is a great assignment and a great way to learn light.
     
  9. Olympus E300

    Olympus E300 TPF Noob!

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    I'm not calling BS here...I'm trying to learn! Lets get the straight right now! With that said, I have a question regarding your 2nd shot. If there is only one light source (800W strobe), then why does each eye show two reflections? Was it bounced? Again...I'm trying to learn - NOTHING more!

    Havings said all of that...I think you have done a mighty fine job here!! The photos look nice. The 1st one is my favorite. Cute child!

    Cheers!!
    - Dan
     
  10. LBPhotog

    LBPhotog TPF Noob!

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    I knew that was going to come up ... look at the first image, there is a catch light in her eye from the windows.

    If you look at the catch lights in the second shot yeah, there are two, one from the window and one from the strobe. But, there is a shadow side on the side opposite the flash, which tells me that there wasn't much, if any, fill let in from the window - I just couldn't eliminate the reflection from her eye and keep the exposure correct.

    if you look at the third exposure there isn't much of a shadow on the back of subject. Which tells me that there WAS some ambient light that hit that exposure ...

    I could be wrong, but that's my understanding of what is going on here. If I am wrong, that is why I signed up for these lessons because I want to further my understanding of light ... :)

    Thanks for the complements Dan, she is cute, and she get's it all from her momma - cause my sorry ass can't produce a child THAT cute. :lmao:
     
  11. Olympus E300

    Olympus E300 TPF Noob!

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    Thanks for the info - I thing I understand. I'm just happy that you didn't think that I was trying to step on your toes! Cheers!!

    - Dan
     
  12. iBats

    iBats TPF Noob!

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    do you know if the pocket wizard plus II will work with the combo of a D3000, SB-600?
     

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